The present invention relates to an improved process for making a copolymer of a polybutene with an unsaturated acidic reagent.
Copolymers prepared from polyisobutene and maleic anhydride are known. These copolymers are sometimes referred to as xe2x80x9cpolyPIBSAxe2x80x9d. They can be prepared by copolymerizing a polybutene containing a high concentration of the methylvinylidene isomer (along with other polybutene isomers) with an unsaturated acidic reagent such as maleic anhydride using a free radical initiator. Apparently, only the methylvinylidene isomer reacts. If the polybutene contains, e.g., 70 mole percent methylvinylidene isomer, then only 70% conversion to copolymer can be achieved. This results in a less than optimum use of the polybutene starting material.
In order to improve the conversion of the polybutene starting material and improve raw material utilization, it has been found that if the polyPIBSA reaction mixture is further reacted with the unsaturated acidic reagent in the presence of a strong acid catalyst, such as a sulfonic acid catalyst, the unreacted polybutene can be converted to polyisobutenyl succinic anhydride. Up to 90-95% conversion of the starting polybutene can be achieved in this way. The resulting product is a mixture of polyPIBSA and acid-catalyzed thermal PIBSA.
The resulting mixture of polyPIBSA and acid-catalyzed thermal PIBSA can then be reacted with amines to form succinimides which can be post-treated with ethylene carbonate, boric acid and the like. These products are excellent ashless dispersants for lubricants with outstanding deposit inhibiting properties, and excellent soot thickening properties, and are also useful as fuel additives.
The present invention provides a process for preparing a mixture of (1) a copolymer of a polyalkene and an unsaturated acidic reagent and (2) a polyalkenyl derivative of an unsaturated acidic reagent, said process comprising:
(a) copolymerizing (1) a polyalkene containing alkylvinylidene isomer and non-alkylvinylidene isomers and (2) an unsaturated acidic reagent under polymerization conditions in the presence of a free radical initiator; and
(b) reacting the product of step (a) with an unsaturated acidic reagent at elevated temperature in the presence of a strong acid.
Preferably, the polyalkene is a polybutene. More preferably, the polybutene is a polyisobutene, most preferably wherein at least 50% of said polyisobutene has methylvinylidene end groups. Preferably, the polyalkene has a Mn of from 500 to 2500.
Preferably, the unsaturated acidic reagent is maleic anhydride.
Preferably, the mole ratio of unsaturated acidic reagent to polyalkene is at least 1.0:1.
Preferably, the strong acid is an oil-soluble, strong organic acid, having a pKa of less than about 4. More preferably, it is a sulfonic acid, such as an alkyl benzene sulfonic acid, wherein the alkyl group has from 4 to 30 carbon atoms. Preferably, the sulfonic acid is present in an amount in the range of from 0.0025% to 1.0% based on the total weight of polyalkene.
The present invention further provides the product produced by a process comprising:
(a) copolymerizing (1) a polyalkene containing alkylvinylidene isomer and non-alkylvinylidene isomers and (2) an unsaturated acidic reagent under polymerization conditions in the presence of a free radical initiator; and
(b) reacting the product of step (a) with an unsaturated acidic reagent at elevated temperature in the presence of a strong acid.
Also provided by the present invention is a composition comprising a mixture of (1) a copolymer of a polyalkene and an unsaturated acidic reagent and (2) a polyalkenyl derivative of an unsaturated acidic reagent wherein the weight ratio of copolymer to polyalkenyl derivative is about 0.1-10. This mixture is referred to herein as a xe2x80x9cpolyPIBSA/acid-catalyzed thermal PIBSA mixturexe2x80x9d.
Further provided by the present invention is a polysuccinimide prepared by reacting a polyPIBSA/acid-catalyzed thermal PIBSA mixture of the present invention with an amine, a polyamine having at least two basic nitrogens, or mixture thereof. The present invention also provides a concentrate comprising 10 to 90 weight percent of such a polysuccinimide and from 90 to 10 weight percent of an organic diluent. In addition, the present invention provides a lubricating oil composition comprising a major amount of an oil of lubricating viscosity and a minor amount of such a polysuccinimide. Also provided by the present invention is a post-treated composition prepared by treating such a polysuccinimide under reactive conditions with a cyclic carbonate. Further provided by the present invention is a post-treated composition prepared by treating such a polysuccinimide under reactive conditions with a boron compound.
The present invention further provides a lubricating oil composition comprising a major amount of an oil of lubricating viscosity and a minor amount of the post-treated composition. Also provided by the present invention is a concentrate comprising 20 to 60 weight percent of the post-treated composition and from 80 to 40 weight percent of an organic diluent.
Also provided by the present invention is a fuel composition comprising a hydrocarbon boiling in the gasoline or diesel range and from about 10 to about 10,000 parts per million of post-treated composition of this invention. Further provided is a fuel concentrate comprising an inert, stable oleophilic solvent boiling in the range of 150-400xc2x0 F. and at least 5 percent by weight of the post-treated composition of this invention.